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3 2 predator cues. Noctuid moths have two auditory receptors (A1 and A2) sensitive to the ultrasonic 3 3 echolocation calls of insectivorous bats. Larger moths are detected at greater distances by bats than 3 4 smaller moths. Larger moths also have lower A1 best thresholds, allowing them to detect bats at 3 5 greater distances and possibly compensating for their increased conspicuousness. Interestingly, the 3 6 sound frequency at the lowest threshold is lower in larger than smaller moths, suggesting that the 3 7 relationship between threshold and size might vary across frequencies used by different bat species. 3 8 Here, we demonstrate that the relationships between threshold and size in moths were only 3 9 significant at some frequencies, and these frequencies differed between three locations (UK, Canada, 4 0 Denmark). The relationships were more likely to be significant at call frequencies used by 4 1 proportionately more bat species in the moths' specific bat community, suggesting an association 4 2 between the tuning of moth ears and the cues provided by sympatric predators. Additionally, we 4 3 found that the best threshold and best frequency of the less sensitive A2 receptor are also related to 4 4 size, and that these relationships hold when controlling for evolutionary relationships. The slopes of 4 5 best threshold vs. size differ, however, such that the difference in threshold between A1 and A2 is 4 6 greater for larger than smaller moths. The shorter time from A1 to A2 excitation in smaller than 4 7 larger moths could potentially compensate for shorter absolute detection distances in smaller moths.